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A048111
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Number of unitary divisors of n (A034444) < number of non-unitary divisors of n (A048105).
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5
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16, 32, 36, 48, 64, 72, 80, 81, 96, 100, 108, 112, 128, 144, 160, 162, 176, 180, 192, 196, 200, 208, 216, 224, 225, 240, 243, 252, 256, 272, 288, 300, 304, 320, 324, 336, 352, 360, 368, 384, 392, 396, 400, 405, 416, 432, 441, 448, 450, 464, 468, 480, 484
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OFFSET
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1,1
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COMMENTS
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Numbers n that are expressible as a product of 2 "non-squarefree" numbers (i.e. there are 2 integers x,y in A001694 such that n = xy) - Benoit Cloitre, Jan 01 2003
Also numbers having more than one square divisor >1: A046951(a(n))>2. - Reinhard Zumkeller, Apr 08 2003
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LINKS
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Table of n, a(n) for n=1..53.
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FORMULA
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A000005(n)>2^(1+A001221(n)).
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EXAMPLE
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a[ n ]= 810 = 2*3^4*5, A001221[ n ]=3, A000005[ n ]=20, A034444[ x ]=2^3=8, nud[ x ]=A000005(n)-A034444(n)= 20-8=12 thus 8<12 and d(n)=20>2^(1+r)=16. 20=d>2^(r+1)=16; U=set is for 810={1,810,2,405,5,162,10,81},notU includes 12 non-unitary divisors.
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CROSSREFS
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Cf. A000005, A001221, A034444, A048109, A082293, A013929, A082294, A082295.
Sequence in context: A059164 A040240 A055075 * A122614 A046101 A044856
Adjacent sequences: A048108 A048109 A048110 * A048112 A048113 A048114
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KEYWORD
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nonn
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AUTHOR
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Labos E. (labos(AT)ana.sote.hu)
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STATUS
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approved
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